Why is my Subaru Forester not starting sometimes?

A Subaru Forester that won’t start intermittently is usually caused by battery or charging issues, ignition or starter faults, immobilizer/key problems, or fuel delivery and engine management issues. Quick checks can help pinpoint the likely culprit.

This article outlines the most common reasons a Forester might fail to start at times, how to test them safely, and when to seek professional help. It covers electrical and security system problems, fuel delivery and engine management, and model-specific considerations that can affect starting reliability.

Immediate checks you can perform

Start with these straightforward checks to rule out obvious faults before moving to deeper diagnostics.

• Battery health and connections: verify the battery voltage (around 12.6 volts or more when the car is off) and check for corrosion or loose clamps on the terminals. A weak battery can cause intermittent starting.


• Starter relay and fuses: inspect the starter relay and related fuses (starting circuit, ignition, and fuel pump). A failing relay or blown fuse can prevent the engine from cranking.


• Transmission and safety switch: ensure the vehicle is in Park (automatic) or Neutral (manual). Some models require the correct position for the starter circuit to engage.


• Immobilizer/key fob status: look for immobilizer indicators on the dashboard and test with a spare key or new key fob battery to rule out security-system issues.


• Crank vs. no-crank symptoms: note whether you hear a click, a slow crank, or no sound at all when turning the key or pressing the start button; this helps distinguish battery, starter, or wiring problems.

If these quick checks don’t reveal a clear cause, continue with more detailed diagnostics or contact a technician for a formal inspection.

Electrical and security system causes

Many intermittent no-start episodes originate in the electrical system or anti-theft components. These issues can be subtle and require careful testing to confirm.

• Battery or alternator failure: a battery that won’t hold a charge or an alternator that isn’t charging can cause the car to stall or fail to start, especially after driving and with heavy electrical loads on.


• Loose or corroded grounds and connections: poor grounding or corroded battery cables disrupt power delivery to the starter, ECU, and sensors.


• Immobilizer/key system problems: intermittent immobilizer recognition or key programming faults can prevent starting; symptoms often include a flashing security light or no crank.


• Ignition switch or wiring faults: a worn ignition switch or damaged harness can fail to send the start signal consistently.


• Starter motor or relay faults: a failing starter motor or a sticking/weak starter relay can cause intermittent cranks or no crank.

Electrical faults can be intermittent and tricky to diagnose. A professional with a diagnostic scanner can verify electrical health, read trouble codes, and test starting circuits safely.

Fuel delivery and engine management

Problems in the fuel system or engine sensors can manifest as starting hesitations or no-start under certain conditions (temperature, fuel level, or load).

• Fuel pump and pressure: a failing fuel pump or clogged fuel filter can prevent adequate fuel delivery, leading to a no-start or hard-start scenario.


• Fuel pressure and leaks: insufficient fuel pressure or leaks in the fuel line can cause starting failures, especially after the engine has warmed or cooled.


• Sensors and ECU interpretation: faulty crankshaft or camshaft position sensors, or other critical engine sensors, can cause the ECU to withhold a start despite key ignition.


• Spark and ignition components: worn spark plugs or faulty ignition coils can prevent reliable ignition, particularly under load or when the engine is cold.


• recalls and software updates: check your vehicle’s VIN for related recalls or service campaigns that could affect starting behavior, including immobilizer or fuel-system updates.

Diagnosing fuel and sensor-related issues often requires a fuel-pressure test, a scan for diagnostic trouble codes (DTCs), and sometimes component testing by a trained technician.

When to seek professional help

If the Forester continues to exhibit intermittent starting problems after these checks, or if you notice symptoms such as persistent no-crank, engine stalling while driving, warning lights, or unusual smells, schedule service with a Subaru dealer or qualified mechanic. Bring notes on when the issue occurs, how it behaves (cranks, clicks, immobilizer light), and any recent repairs or changes. A professional technician can perform in-depth electrical tests, fuel-system diagnostics, and, if needed, software updates or recalls.

Summary

Intermittent starting trouble in a Subaru Forester is most often related to the battery and charging system, immobilizer or key issues, ignition or starter faults, or fuel delivery and engine-management problems. Begin with simple checks of the battery, connections, fuses, and security indicators, then move to more detailed electrical and fuel-system diagnostics if needed. Persistent or unclear results warrant a professional diagnostic to prevent being stranded and to ensure safety.

Why does my Subaru not start sometimes?

Here are a few reasons why your Subaru might not start, even with a good battery: Bad battery cables or loose clamps: If the cables are loose or corroded, power can't reach the starter. Even a strong battery won't help. Worn starter motor: If the starter is failing, the engine won't turn.

What does it mean if your car doesn't start sometimes?

A car may fail to start sometimes due to electrical issues like a dead or loose battery connection, a faulty starter motor, or a bad alternator. Other common reasons include problems with the fuel system (like a clogged filter or weak fuel pump), a faulty ignition switch, or a stuck steering lock. 
Electrical system problems 

• Dead or weak battery: The most common cause. A battery can be drained by leaving lights on or can simply be old. 
• Bad battery connection: Corroded or loose battery terminals can block the flow of power to the starter, even if the battery has a charge. 
• Faulty alternator: The alternator charges the battery while the engine runs. If it's failing, the battery may not get recharged and can die. 
• Failing starter motor: The starter uses a lot of power to crank the engine. If it's bad, you might hear a clicking sound or nothing at all when you turn the key. 
• Blown fuse or relay: A blown fuse or bad relay can cut power to the starter or fuel pump. 

Fuel and air system problems 

• Clogged fuel filter: A clogged filter can prevent enough fuel from reaching the engine. 
• Faulty fuel pump: If the fuel pump is failing, it may not be able to supply enough fuel pressure to start the car. 
• Low fuel: It seems simple, but running out of gas will prevent the car from starting. 

Other common issues

• Faulty ignition switch: A failing ignition switch can prevent power from getting to the starter and other components. 
• Stuck steering lock: If the steering wheel is turned while the key is out, the lock can jam. This can prevent the key from turning to the "start" position. 
• Anti-theft system: An activated immobilizer or anti-theft system can prevent the car from starting. 

Why is my Subaru Forester struggling to start?

A Subaru Forester struggling to start is most likely due to a weak battery or poor battery connections. Other common causes include a failing starter motor, an issue with the fuel system (like a weak fuel pump or clogged injectors), or a problem with the ignition system (like bad spark plugs, coil packs, or ignition switch). 
Common causes and troubleshooting steps
This video explains some common causes for a Subaru Forester struggling to start: 54sKurt of TradesYouTube · Mar 17, 2022

• Battery issues: A weak or old battery can't provide enough power, leading to slow cranking or no start. 
  • Check: Make sure the battery terminals are clean and the connections are tight. 
  • Test: Have a technician test the battery's health, especially if it's over 5 years old. 
• Starter motor problems: The starter motor may be failing, causing slow cranking or a "click" sound when you turn the key. 
  • Check: If the dashboard lights are on but the engine won't turn over, the starter could be the issue. 
  • Test: A professional can test the starter for proper engagement. 
• Ignition system issues: Worn spark plugs, faulty coil packs, or a bad ignition switch can prevent the engine from starting, as they are needed to ignite the fuel. 
  • Check: Inspect spark plugs and ignition coils. These may need to be replaced, especially if they are old. 
  • Test: A mechanic can use diagnostic tools to check the ignition system for proper function. 
• Fuel system problems: A weak fuel pump or clogged fuel injectors can lead to hard starting or the engine shutting off. 
  • Test: This is best diagnosed by a professional who can check fuel pressure and injector function. 
• Other potential causes:
  • Key fob or security system: A weak battery in the key fob or a security system malfunction can prevent the car from starting. 
  • Vacuum leaks: A leak in the air intake system can cause a lean air-fuel mixture and starting problems. 
  • Incorrect gear: Ensure the vehicle is in Park or Neutral, as the shift interlock system will prevent starting in the wrong gear. 

Next steps

• Start with the basics: First, check your battery terminals and try a jump-start to see if a dead battery is the immediate problem. 
• Seek professional help: If simple checks don't work, consult a mechanic. They can use diagnostic tools to pinpoint issues with the starter, ignition system, fuel system, or security system. 

You can watch this video to see a demonstration of a diagnostic tool being used: 18sRomano's AutomotiveYouTube · Aug 14, 2024

Why is my Subaru Forester not starting?

A Subaru Forester won't start due to a dead battery, starter issues, or problems with the ignition or immobilizer system. Check for a clicking sound or dim lights to diagnose a weak battery, but if the lights are on, the issue could be the starter, ignition switch, or immobilizer system. You can also check your key fob's battery for push-start models, and try shifting the gear selector to Neutral to rule out a neutral safety switch issue.
 
This video explains how to start a Subaru with a push-button start if the key fob battery is dead: 39sCopeland Subaru HyannisYouTube · Nov 1, 2024
Common causes and what to check

• Weak or dead battery: This is the most common reason. 
  • What to look for: A clicking sound when you turn the key, dim dashboard lights, or the engine not cranking at all. 
  • What to do: Try a jump-start. If it starts, your battery is likely the problem and needs to be replaced. Also, check the battery terminals for corrosion or looseness. 
• Starter motor or relay failure: The starter motor sends the engine a crank, and the relay is a part that sends power to it. 
  • What to look for: The engine may not crank at all, or you might hear a single click when trying to start. Dash lights may still turn on. 
  • What to do: A faulty starter relay or a bad starter motor can prevent the engine from cranking even if the battery is good. 
• Ignition switch or immobilizer system: These systems can fail and prevent the car from starting. 
  • What to look for: The engine won't crank, but the dashboard lights may flicker or dim. The immobilizer system may not recognize the key. 
  • What to do: For push-start models, check if the key fob battery is weak and try holding the fob against the start button. You may also need to have the system scanned for error codes. 
• Neutral safety switch: This switch prevents the car from starting unless it's in Park or Neutral. 
  • What to look for: The car won't start in Park. 
  • What to do: Try starting the car in Neutral. If it starts, the switch may be faulty or misaligned. 
• Fuel system issues: The engine cranks but doesn't start. 
  • What to look for: The engine turns over but won't catch and run. 
  • What to do: This could indicate a problem with the fuel pump or fuel filter. It is best to have this diagnosed by a professional. 
• Power steering pump: On some models, a failing power steering pump can cause the engine to stall. 
  • What to look for: A seized power steering pump can prevent the engine from starting. 
  • What to do: If you suspect this is the issue, it may require professional diagnosis.